Search

Metals discharged from abandoned mines are a major source of pollution in many parts of the world. As a result, there is a growing need for suitable low-cost remediation methods. While a large literature base exists demonstrating the efficacy of biochar to remove metals from solution, most studies are confined to the laboratory. This study examines the effects on the biochar quality when scaling up production from laboratory to pilot scale. Pilot scale biochars were produced using a 600 kg batch pyrolysis reactor, these chars were then deployed in the field using a series of 100 mm × 1200 mm cylindrical treatment cells installed at the point of discharge from an abandoned mine site. Most biochars produced at a pilot removed more zinc under laboratory conditions, however all of the biochars showed a reduced performance when tested in the field, this ranged from a 14% to an 85% reduction depending on the biochar., (Crown Copyright © 2022. Published by Elsevier Ltd. All rights reserved.)

Soils in the Lower Swansea Valley, (United Kingdom) contain elevated level of metals, enough to cause direct or indirect effects on human health. This study assesses the severity of soil pollution and bioavailability of Cu and other metals (Ni, Zn, Co, Pb and Cr) in soils with various distances from a Ni refinery. We compare Cu concentrations in operationally defined soil fractions (bioavailable, bound to Fe/Mn oxide and incorporated in organic matter) with other metals (Ni, Zn, Pb, Co, Cr) usually occurring in ores used in metallurgic processes and report their pollution and geoaccumulation indices (PI and I geo ). Further, we use Cu stable isotope ratios (δ 65 Cu) to trace the fate and mobility of Cu in soils. Our data suggest a point source of contamination for some of the heavy metals including Ni (I geo  = 1.9), Zn (I geo  = 0.28) and Cu (I geo  = 3.6) near the Ni refinery. However, Co (I geo  = 0.15) and Pb (I geo  = 3.3) contaminations are likely to be linked to different sources. No elevated Cr levels (I geo = -0.07) occur in any of the studied soils. All soil metals are predominantly associated with organic matter (>50%) which  reduces their bioavailibility and thus their risk for ecological and human health. The Cu isotope data show that Cu in soil organic matter is enriched in 65 Cu, while the lighter isotopes ( 63 Cu) remain in the dissolved bioavailable Cu fraction (Δ 65 Cu organic-bioavailable is +0.12 ± 0.13‰). This suggests the preferential complexation of 65 Cu with soil organic matter after dissolution of Cu deposited to the soil. Thus, Cu isotope data can effectively indicate pathways of metal migration in polluted soils., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature.)

Mine tailings represent a globally significant source of potentially harmful elements (PHEs) to the environment. The management of large volumes of mine tailings represents a major challenge to the mining industry and environmental managers. This field-scale study evaluates the impact of two highly contrasting remediation approaches to the management and stabilisation of mine tailings. The geochemistry of the tailings, overlying amendment layers and vegetation are examined in the light of the different management approaches. Pseudo-total As, Cd and Pb concentrations and solid-state partitioning (speciation), determined via sequential extraction, were established for two Tailings Management Facilities (TMFs) in Ireland subjected to the following: (1) a 'walk-away' approach (Silvermines) and (2) application of an amendment layer (Galmoy). PHE concentrations in roots and herbage of grasses growing on the TMFs were also determined. Results identify very different PHE concentration profiles with depth through the TMFs and the impact of remediation approach on concentrations and their potential bioavailability in the rooting zone of grass species. Data also highlight the importance of choice of grass species in remediation approaches and the benefits of relatively shallow-rooting Agrostis capillaris and Festuca rubra varieties. In addition, data from the Galmoy TMF indicate the importance of regional soil geochemistry for interpreting the influence of the PHE geochemistry of capping and amendment layers applied to mine tailings.

Elevated levels of selenium (maximum 200 mg/kg) and tellurium (maximum 11 mg/kg) are reported in topsoils (<5 cm) from around a long-established nickel refinery at Clydach in the Lower Swansea Valley, UK. Se and Te are correlated with each other and when these data are plotted as contour diagrams they show a concentric pattern centred on the refinery site. The origin of the Se and Te contamination is investigated. A review of the changes in the refinery practices at the site is presented and used to link the soil contamination to industrial pollution which took place over 80 years ago. The most recent air quality data available cannot rule out some Se contamination up to 2003., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Green rust, an Fe (II) and (III) oxyhydroxy salt, can alter the aqueous oxidation state, mobility and toxicity, of inorganic contaminants and thus could have applications in water treatment. This paper discusses a series of stirred, open batch experiments designed to evaluate green rust, and its oxidised equivalent in this context comparing it to a ferrihydrite/goethite 'ochre'. Natural green rust was added to different mine waters as either a wet, reduced material or a dry, partially oxidised material. Experiments showed that the addition of either form accelerated the removal of potentially harmful elements from solution. Within one hour Fe, Al and Cu were completely removed from mine waters with initial concentrations of 80, 70 and 8.5mg/L, respectively, and Zn was reduced from 60 to <5mg/L. These experiments show the potential of green rust in mine water treatment, especially as it is able to remove problematic elements such as Al and Zn. The material is effective even after being dried and mostly oxidised. Changes to the pH and ORP of the mine waters and surface catalysis are the suggested mechanisms of accelerated removal of contaminants., (Copyright © 2011 NERC. Published by Elsevier B.V. All rights reserved.)

The diversity of highly active bacterial communities in cryoconite holes on three Arctic glaciers in Svalbard was investigated using terminal restriction fragment length polymorphism (T-RFLP) of the 16S rRNA locus. Construction and sequencing of clone libraries allowed several members of these communities to be identified, with Proteobacteria being the dominant one, followed by Cyanobacteria and Bacteroidetes. T-RFLP data revealed significantly different communities in holes on the (cold) valley glacier Austre Brøggerbreen relative to two adjacent (polythermal) valley glaciers, Midtre Lovénbreen and Vestre Brøggerbreen. These population compositions correlate with differences in organic matter content, temperature and the metabolic activity of microbial communities concerned. No within-glacier spatial patterns were observed in the communities identified over the 2-year period and with the 1 km-spaced sampling. We infer that surface hydrology is an important factor in the development of cryoconite bacterial communities.

Unlike organic pollutants, heavy metals cannot be degraded and can constitute a persistent environmental hazard. Here, we investigated the success of different remediation strategies in promoting microbial diversity and function with depth in an acidic soil heavily contaminated with Cu, Pb and Zn. Remediation involved the incorporation of either a high- or a low-quality compost or inorganic fertilizer into the topsoil and monitoring of microbial activity and diversity with soil depth over a 4-month period. While changes in topsoil microbial activity were expected, the possible effects on the subsurface microbial community due to the downward movement of metals, nutrients and/or soluble organic matter have not been examined previously. The results showed that both compost additions, especially the low-quality compost, resulted in significantly increased bacterial and fungal diversity (as assessed by terminal restriction fragment length polymorphism) and activity compared with the inorganic and control treatments in the topsoil. Although phospholipid fatty acid profiling indicated that compost addition had promoted enhanced microbial diversity in the subsoil, no concomitant increase in subsoil microbial activity was observed, suggesting that amelioration of the heavy metals remained localized in the topsoil. We conclude that although composts can successfully immobilize heavy metals and promote ecosystem diversity/function, surface incorporation had little remedial effect below the surface layer over the course of our short-term trial.

Soils contaminated with heavy metals can pose a major risk to freshwaters and food chains. In this study, the success of organic and inorganic intervention strategies to alleviate toxicity in a highly acidic soil heavily contaminated with As, Cu, Pb, and Zn was evaluated over 112 d in a mesocosm trial. Amelioration of metal toxicity was assessed by measuring changes in soil solution chemistry, metal leaching, plant growth, and foliar metal accumulation. Either green waste- or MSW-derived composts increased plant yield and rooting depth, reduced plant metal uptake, and raised the pH and nutrient status of the soil. We conclude that composts are well suited for promoting the re-vegetation of contaminated sites; however, care must be taken to ensure that very short-term leaching pulses of heavy metals induced by compost amendment are not of sufficient magnitude to cause contamination of the wider environment.

Potato dextrose agar (PDA) is one of the most commonly used media for the isolation and cultivation of fungi, with morphological features and pigmentation in culture often being important for identification of cultures. Cultivation of various fungi on different brands and batches of powdered (commercial) potato dextrose media revealed deficient pigmentation in five of 10 media tested. Reduced pigmentation on these media was correlated with low levels of copper and colony colour was restored by the addition of copper. Deficient pigmentation was most pronounced when copper levels in the medium were below 50 ng mL(-1) (50 p.p.b.; 0.8 microM). Differences in pigmentation and laccase activity of spore and mycelial preparations were quantified for representative species belonging to the genera Aspergillus, Fusarium, Trichoderma, Cladosporium and Penicillium grown on PDA containing different amounts of copper. A strong positive correlation between laccase activity and copper levels was observed. Differences were also found between batches of raw potatoes, with organically cultivated tubers having higher copper levels than those grown by conventional methods, possibly because of the use of copper-based fungicides in the former case. Routine addition of 1000 ng mL(-1) copper (or standard trace element solutions) to PDA and other undefined media is advised to avoid atypical culture pigmentation and possibly other consequences of reduced activity of copper-requiring enzymes.

The presence of the radionuclide (99)Tc in the marine environment is of concern to environmental scientists because of its conservative nature and high concentration factor in commercially valuable species. The brown seaweed Ascophyllum nodosum (Linnaeus) Le Jolis was used to biomonitor the spatial distribution of (99)Tc around the Welsh coast, an area relatively unstudied with respect to this isotope. Over the course of a year an inverse relationship was observed between the (99)Tc concentration in A. nodosum samples and approximate straight-line distance from Sellafield. These data show that detectable levels of a Sellafield derived radionuclide are reaching the Welsh coast despite the overall northward movement of the Sellafield plume.

Aluminium in water supplies derives from natural sources and from the use of Al2(SO4)3 in water treatment. Heavy metals such as Pb, Cu, Zn and Cd can be added to water from pipework and solder. However, it is apparent that AI and other metals in potable waters can derive from deposits on pipe walls which can be subsequently mobilised when the supply and/or treatment process is changed. Concentrations of Al in domestic supply water of the Llanbrynmair area have been shown to increase from 1 μg to 50 μg L(-1) during its 18 km journey along the water main. Similarly, Pb concentrations in a public building in the Aberystwyth area are found to be extremely elevated due to the metal's mobilisation from encrustations occurring on the copper pipework.

Topsoiis in the Mendip Hills of north Somerset are strongly enriched in Pb, Zn and Cd. While much of this enrichment is the result of pollution stemming from previous base metal mining, analyses of soil profile samples reveals that, in several cases, there is considerable enrichment of heavy metals with depth. This, together with relatively high levels of base metals in samples of the limestone and sandstone bedrocks, suggests that some of the enrichment in soil of heavy metals is due to natural processes.

The many abandoned base metal mines of the mid-Wales ore field are sources of extensive pollution. Some of the mineralised veins contain large amounts of pyrite and marcasite and oxidative weathering of these produces sulphuric acid resulting in very acidic mine drainage waters. In addition, the spoil tips associated with these mines can contain abundant iron sulphides. Drainage waters from these sources have pH values as low as 2.6 and are heavily contaminated with metals such as Al, Zn, Cd and Ni.Two of the main rivers of the area, the Rheidol and Ystwyth, intercept heavily contaminated acidic drainage which has a marked effect on water quality. The Rheidol contains over 100 μg L(-1) Zn for 16 km downstream of the acid water influx. This level is over three times the recommended EEC limit for Zn in salmonoid waters of low hardness.